Any chance of returning seasonals?

Seasonals return during legendary hero banners, so they do return, but i'm not sure if W!Lissa has been in one yet

A rotation of Seasonals can be summoned in Legendary Banners. Recently, the first Spring banner also returned for the previous gauntlet. So yes.

Winter Lissa will become available again in a future Legendary banner, so you still have time.

I expect a Groom Banner with all males in groom outfits, those who are counterparts to the Bridals: Marth (Caeda), Xander?(Charlotte), Chrom(Cordelia), and Hector/Eliwood(Lyn). Then after that, we meet the Brides again for a Voting Gauntlet.

Absolutely, just be patient. A few are released every legendary banner and recently last year's spring banner resurfaced alongside this year's new spring banner. I believe the pattern of legendary banner releases are in chronological order, and with the most recent one we just hit the Halloween units, so I expect to see Christmas units in 2 or 3 legendary banners from now. Otherwise wait until next Christmas :) Hope this helps.

You’re only hope to get the seasonal unit you want was that if they appear in a legendary banner.